Comparison between Equilibrium Model and Rate-Based Model for Simulation of Batch Zeotropic Distillation

Abstract

In this work two models (equilibrium and nonequilibrium) have beendeveloped to study the dynamic behavior of multicomponent zeotropic(nonazeotropic) system in batch distillation column. The results of the two models were compared with the experimental results in order to construct and develop an improved dynamic model. The experimental work was performed through using a batch distillation column consisting of eight bubble-cap trays. zeotropic system of Benzene, Toluene, and Ethylbenzene (B-T-EB) has been used. The equilibrium model is based on MESH equations (Material, Equilibrium relation, Summation of composition, and Heat balances). While the Nonequilibrium model (or Rate-Based model), is based on MERSHQ equations (Material, Energy balances, Rate of mass and heat transfer, Summation of composition, Hydrodynamic equation of pressure drop, and eQuilibrium relation).It was concluded that both models give an acceptable agreement withexperimental results. But nonequilibrium model required many correlations to describe the physical properties which do not exist for all systems. Also the time required to operate the program for nonequilibrium model is more than 100 times than that required to operate equilibrium model.

Keywords

• batch distillation
• equilibrium
• nonequilibrium